German Patent Application No. DE 100 22 815 describes a device in which the signal of a knock sensor is converted from analog to digital and the further processing of the knock data is then implemented on the basis of these digital data. Monitoring of the knock control is provided as well, which is based on the feeding of test signals and a check as to whether a corresponding knock level that matches these test signals is produced. Evaluation of the digital knock data for monitoring purposes is not provided.